With the S&P 500 and Dow Jonespulling back from their all-time highs, investors are starting to worry that bulls are losing momentum.

And there are plenty of reasons to worry.

The wholesale price of gasoline is up 14 percent so far this month and pundits are starting to think it's going to pinch the consumer and dampen the recovery. "The Street thinks the increase is akin to a tax, a direct tax that takes disposable income and flushes it down the toilet," Cramer said.

Also Ben Bernanke's testifies on Wednesday before the House Financial Services Committee. His comments will be closely analyzed for signs of when the central bank may start reducing its stimulus efforts. If the Street thinks the Fed is a step closer to tapering, rates could spike, "and you remember what happened in the market the last time rates spiked," Cramer said.

Again, there are plenty of reasons to worry. It seems to make perfect sense to conclude that the stock market could be topping out.

Except, for one thing.

"There's been plenty to worry about for months," Cramer reminded. "There's been plenty to worry about since the beginning of the year."

"As it turned out, investors who sold stocks due to these kinds of developments worried too much," he said. That is, investors who cashed out of the market when rates spiked or violence broke out overseas missed out on subsequent gains.

Cramer thinks the best way to prepare for a possible sell-off is to make a list of favorite stocks and buy strategically. "History suggests to me buying a decline would be the rational thing to do, and, in the end, doing what's rational makes the most money. Worrying is rarely rational."